#include<iostream>
using namespace std;
int n, m, xh, yh;
long long pand[30][30]={0}, f[30][30]={0};
int main()
{
	cin >> n >> m >> xh >> yh;
	n += 2;
	m += 2;
	xh += 2;
	yh += 2;
	for (int i = 2; i < 30; i++) {
		f[2][i] = 1;
		f[i][2] = 1;
	}
	pand[xh][yh] = 1;
	pand[xh - 1][yh - 2] = 1;
	pand[xh - 1][yh + 2] = 1;
	pand[xh - 2][yh - 1] = 1;
	pand[xh - 2][yh + 1] = 1;
	pand[xh + 1][yh - 2] = 1;
	pand[xh + 1][yh + 2] = 1;
	pand[xh + 2][yh - 1] = 1;
	pand[xh + 2][yh + 1] = 1;
	f[1][2] = 1;
	for (int i = 2; i <= n; i++) {
		for (int j = 2; j <= m; j++) {
			f[i][j] = f[i - 1][j] + f[i][j - 1];
			if (pand[i][j] == 1) {
				f[i][j] = 0;
			}
		}
	}
	cout << f[n][m] << endl;
	return 0;
}